One of the most commonly reported experiences associated with SP is that of the sensed presence. It is also the least specific and perhaps most fundamental experience of the HHEs, one that may serve as a primary source of the development of elaborated interpretations associated with incubus attacks, the old hag, and alien abductions. The notion of a sensed presence is not unique to SP. Virtually everyone has, at some time, had the experience of feeling that he or she was not alone, despite fairly confident knowledge that there really was no other person around. Sometimes, in the absence any perceptible evidence, one has a feeling that there is someone, or something, close at hand (Reed, 1988; Zusne & Jones, 1982). This feeling may range from a vague, almost embarrassing, suspicion to a feeling of absolute certainty. We commonly associate such feelings with the dark and with strange surroundings, and, of course, being alone. We may have also experienced a presence when walking alone on a dark street, or through a woodlot, or even being home alone, especially if it is a "dark and stormy night" filled with vague rustlings, howling winds, squeaking shutters, and distant animal sounds. Reed (1988) describes the experience of a Professor Collie, alone at the summit of Ben Macdhui (which is described as a "snowy, featureless" peak) in the Cairngorm peaks in Scotland, hearing footsteps in the snow and becoming convinced that somebody or something was present with him. This feeling became so intense that he fled in panic. From that time, this invisible spectre has troubled many hikers on Ben Macdhui. Reed argues that this is a concrete, documented historical example of the process by which legends arise from an experiential base.
The terror that accompanies such a presence is extremely common. The sensed presence and fear are so closely connected that it is difficult, in these circumstances, to sort out whether the presence brings the fear, or whether fear and apprehension generate the sense of presence, or whether they simply arise together in intimidating contexts. Indeed, the circumstances giving rise to these experiences are so clearly fear provoking and are such plausible conditions for assailants of all stripes that it seems not unlikely that both might arise independently.
The Phenomenology and Ontology of Presence
On reflection, the notion of pure presence is very odd to contemplate. If you were here I could see you, hear your voice, and touch you. My sense of your presence would seem to be the sum total of all of this evidence of my senses. That I would have, in addition to all of this an experience of your presence-of your existence-seems superfluous. That I would have some need of a sense of your presence without the evidence of my senses seems very unproductive. Yet, experience of the "sensed" presence would seem to argue that there is indeed something over and above the sum of our sensory experiences.
Perhaps the phrase, "sensed presence" is an oxymoron, for there is no sensory evidence of the presence-and yet it is apprehended. To say that it is "unsensed" seems even worse. It is more of an intuition of a presence. Perhaps it would be best to call it an "experienced presence, " or an experience of a presence." It is an experience without a modality, neither seen nor heard, nor able to be touched. In any case these terms are awkward if, perhaps, somewhat more accurate. We will accept a modicum of incongruity and continue with the phrase, "sensed presence" and acknowledge that that it not sensory in the usual meaning of having a particular modality.
Is the sensed presence a hallucination? It clearly lacks the central requirement of discrete sensation. The sensed presence is more like a simple awareness or apprehension of a person or thing in the room. Yet there is the conviction that the entity exists outside and independently of the person. Even without further auditory, tactile, or visual sensations it often has more than the feeling of a mere suspicion or hunch. The sense of presence may be very strong and it clearly seems to be quite real, external, and independent. Yet, for all that there remains a sense that there is indeed a feeling of "seeming" to all this, possibly, at least in part, because of a lack of confirmation from any specific modality. In some cases the presence may be described as "invisible." However, most often it is simply "unseen," that is, respondents report the impression that the presence is "just out of sight." If only one could turn around it would prove to be quite visible
Often the sensed presence is described as just that, a neutral, or perhaps slightly uneasy, feeling that someone or something is present in a room or surrounding area with the person. As a "mere presence" this experience has no sensory associates, nor does it provoke a strong emotional reaction or complex interpretations. One has the definite impression that there is something external to oneself yet with no confirming sensory experience of that entity.
As noted above the sensed presence is not a part of everyone's SP experience. Moreover, those who do report the sensed presence do not report having the experience every time. "1/3 of the occasions through my life, the disturbance has been accompanied with a feeling of a presence in my bedroom. A great fear usually overcomes me, but only about a 1/3 of the events do I feel a presence." The foregoing quote also illustrates the sense of fear that often accompanies the sense of presence. The association between the sense of presence and fear will become increasingly evident as we proceed. This may also be experienced as a feeling of threat or domination. "The sensation is of a presence which is more powerful than me and dominates completely."
The presence associated with sleep presence may also be endowed with certain minimal "psychological" qualities such as that of attention. The presence is often somehow attending to, watching, or monitoring the subject. It is "as if someone that I couldn't see was there, watching." One of the most common comments about the SP experience is that "It feels as if someone is standing there watching me." Respondents are frequently puzzled that they are unable to specify how they know this or even where precisely they think the presence is located. "You feel that someone is looking at you and you don't know where they specifically are." Aside from being very disconcerting this must certainly contribute to the otherworldly sense of the presence. In slightly stronger terms other respondents will describe the presence as "staring at," rather than merely watching, them.
The sensed presence may form the core of subsequent hallucinations involving several modalities. The sensed presence may form the core of subsequent hallucinations involving several modalities. Although very few people actually make the suggestion spontaneously, one respondent was quite specific about the transformation. "The unseen presence starts to emerge as a formed being." Since the presence is usually perceived of as threatening, the interpretation is usually of a presumably readily available innate, "prepared," or conventional image of image of something mysterious and threatening.
The presence is not always immediately interpreted as something bizarre or frightening. Occasionally, the presence is thought to be someone who might plausibly be thought to be ready to hand.
Most of these experiences are reasonable attempts to interpret a feeling that someone or something is present in the room. Sometimes the presence may be associated with sensory experiences. During one of my own experiences, I sometimes thought my wife had come into the room, but subsequently realized that she was not there at which time the presence rapidly turned into a sinister presence. In this case I had been making a low moaning sound in an attempt to alert her to my condition. After a few moments I heard footsteps coming up the stairs, along the hall, and into the room. I inferred was that it was my wife approaching. The footsteps appeared to stop at the side of the bed and I waited for her hand to shake my shoulder. When this did not happen I realized that she was not there and, on reflection, realized that she was not even in the house. I was then immediately filled with a sense of dread and formed a distinct awareness of a sinister presence in the room. In this case the sense of a sinister presence was associated with, and seemed to be caused by, the auditory experiences.
A similar experience involving the hallucination of someone approaching
to arouse one from SP was reported by one of the respondents. In the following
case we also have an illustration of the interaction (and confusion) between
endogenous and exogenous sources, and between illusion and reality, that characterize
the HHEs of SP.
The oddest experience I've ever had was the last episode I had. My boyfriend was watching TV in the living room and I was taking a nap on my couch, I was going through SP but decided to wait it out. All of a sudden I felt a presence behind me. It was making horrifying sound (I thought Death himself came to visit me). I realized my mouth had a little opening. I started to breathe as hard as I could to get my boyfriend's attention. It worked. He sat next to me. I was so relieved that for the first time I had reached somebody while I was in this phase. I thought he touched me on the forehead so that I could be released from the SP but it was my imagination that thought he touched me. When I realized he didn't touch me I started breathing hard again. Right after that, I got out of the SP and saw my boyfriend next to me. I asked him why he didn't touch me when I was panting in my sleep. He thought I was having a bad dream.
Very often, however, the presence is associated with threat and menace. The threatening presence is not always subject to bizarre or otherworldly interpretations. Often people make very plausible assessments of the situation in terms of conventional sources of danger.
Sometimes, in these situations, I feel like there might be a prowler in
the house, even though I know this is impossible.
I constantly think that there are 'bad' people (such as burglars, rapists, etc.) in the room with me.
The second episode I ever had involved a strange man sitting on the edge of my bed. The room was dark, but my eyes were open and I was terrified that there was someone in my room (or so I thought).
Even with no further information or untoward incidence, many respondents appear to have an immediate intuition that the presence is someone or something to be feared. "The presence brought fear with it." The presence is commonly interpreted as possessed of a malevolent, evil intent. Some descriptions never become elaborated beyond a sense of dread, and a fear of impending doom and even death, provoked by this evil presence. "It felt like something threatening was standing beside me." A feeling of urgency and flight may accompany the feelings of fear. "I always feel like I am in grave danger if I don't wake myself up as soon as I can." The presence may even be personified as death. "I've also feel a presence but never see it. Like Death was breathing down my back." The presence may be rendered even more concrete. "My only thought of death was not from my paralysis, rather, from my fear of the 'reality' of my visitor's presence-I thought 'My God! What is this sicko going to do?!?'" We have been especially struck with the frequency that the specific term "evil" is applied to this presence, even by people to whom this term does not readily spring to mind.
The sense of evil is often made concrete by the experience of the presence as a devil, demon, or other inhuman, even unnatural, creature.
Often people run quite explicitly through a series of possibilities, alternating between considering mundane and exotic, vague and specific, and benign and frightening, possibilities. It is also clear that these alternatives are often entertained as possibilities, as hypotheses with varying merits. Some or all of these hypotheses may be recognized and identified as preposterous or at least extremely unlikely. Such assessments do not, however, necessarily detract from the vividness or compelling nature of the experiences. As one respondent put it, the experience is "100% REALISM. But makes no sense." The entire affair is, experientially, utterly compelling, while at the same time capable of interpretation only in terms that are often quite unbelievable. In some case there appears to be a blurring of sensed presence and visual hallucinations.
Not surprisingly, some women experience not only the threat of rape but sometimes also rape itself. Occasionally, the presence is a bit more active, moving about but usually remaining close to the person. "Once, I felt as if someone were walking around my bed, and then they sat down next to me." Or worse, The threat becomes more concrete.
One major difference between SP with HHEs and dreams is the relatively high rate of reporting fear during the former. McCarley & Hobson report that only slightly more than 12% of dream reports make reference to emotions, although half of these were to fearful emotions. More recently Hobson and his colleagues have reported much higher proportions (95%), presumably as a result of using specific probes for emotion (Merrit, Stickgold, Pace-Schott, Williams, & Hobson, 1994). In that study slightly less than one-third of the reports were of anxiety or fear. In contrast, we have found that, depending on the sample characteristics, between 66% and 98% of reports of SP report experiences of fear. The higher percentage was reported by unsolicited responses to a web survey and may be biased by the fact that people who have had more frightening experiences during SP were more likely to seek out the questionnaires. The other samples were not self-selected and this bias would not have been present. Nonetheless, the estimates of two-thirds are considerably higher than those reported for dreams in general and consistent with the rate of 67% reported for SP by Spanos, McNulty, DuBreuil, Pires, Burgess, (1995). Given the prevalence of interpretations of threat and evil associated with the sensed presence it is scarcely surprising that the predominant emotion is that of fear, or rather, in the words of one respondent, "absolute cold terror." Respondents are often most emphatic about the extreme nature of their fear,
These experiences of dread and terror associated with the sensed presence are also clearly different from fear associated with specific fears of paralysis, death, or suffocation. "I have had paralysis, where by I had difficulty breathing that was not associated with a presence and I felt like I might die. Or an urgency to wake up and if I didn't I might die... however, these experiences are distinct and different than the experiences of having a presence in the room." Although the fear may sometimes be ascribed to the fear of the paralysis itself, or that the presence will cause physically harm, many acknowledge that there is something uncanny about the sense of dread. "I literally fear for my soul."
Auditory experiences are much more common than visual experience during SP, although both are significantly associated with the sensed presence. The association between sensed presence and auditory and visual hallucinations is only slightly consistent than that between sensed presence and fear. In general, visual hallucinations are probably quite rare outside of dreaming. Auditory hallucinations during SP are extremely diverse. Two qualities do seem to pervade all of this diversity, however. The sounds are very distinctly experienced as being external to the hearer rather than "in the head." Baillarger, a student of Esquirol, (1846), distinguished between purely "psychic" and "psych-sensorial" auditory hallucinations. The former appears to correspond to "inner speech", is more thought-like, and may be taken to be self-generated. The latter seem to be more like "hearing voices," to be heard by, what St. Teresa referred to, as the "bodily ears," and not likely to be taken to be self generated (Johnson, 1978). More recently, Symons (1995), following Seligman & Yellen (1987), has distinguished between hallucinatory and non-hallucinatory (conjured) imagery. In contrast to dreams the auditory experiences associated with SP are overwhelming of the former "hallucinatory" type.
Sounds - elementary. Very often the auditory experiences are described only as "buzzing," "grinding," "humming," "ringing," "roaring," "rushing," "screeching," "squeaking," "vibrating," "whirring," "whistling," sounds. These are sometimes accompanied by bodily sensations described as "tingling," "numbness," or "vibration." There may be some synesthesia being experienced here. These elementary sounds are often described as being very loud and "mechanical." There is little or no interpretative elaboration of these sensatations. They are described is the most basic sensory terms available to the respondents.
During the waking episodes I don't recall any sounds, but during the hypnagogic
ones I get a loud rushing sound in my ears. Something like it sounds like
when you put your fingers in your ears only it is very loud.
Sounds crescendo as the apparitions approach me. Whirling/ringing noise, sometimes gets unbearably intense. Once I thought my window fan was 'roaring'- the pitch gets higher sometimes, too.
Yes, during the 'buzz' which precedes or accompanies SP. I have heard resonating vibrations (at different frequencies) and arrhythmic percussion, including bells.
A high, humming sound that gets louder and louder the farther I fall into the 'trance'.
On one occasion upon waking up in a paralysis, I heard pure tones of sound, but it
wasn't music. It was very erratic and unorganized.
These particular auditory experiences are very similar to what some people describe as bodily sensations.
Usually when waking up, also usually accompanied by INTENSE bodily vibrations.
I feel like my body is shaking like I am having a seizure or something.
Right as it starts, I feel like I'm being electrocuted slowly.
[bodily] tingling and vibrating
Right as it starts, I feel like I'm being electrocuted slowly.
My whole body felt like it was vibrating inside at some incredible rate. I was afraid that my body and my brain would not physically be able to stand it.
I also felt a numbness and electrical vibration, and would feel stuck to my bed.
Like electricity going through my head
Maybe I might feel numb. It's really hard to tell when you can't move if you're numb or not. I definitely don't feel any tingling.
vibration in my hands is painful if prolonged
I have frequent thought that the bed was being shaken.
One person explicitly made such a connection. In responding to a question about sounds this person remarked that it was "More of a bodily buzzing and swirling." Another suggested that "It's not exactly a sound. I felt a vibration inside my head that produced a noise. I felt as if satellite had been connected to my head. The vibration increases and don't stop until I manage to move. The last time it happened, it affected my left ear and I felt pain, as if my ear would blow up. The pain lasted for two days.
Sounds-Technological. Many of these sounds are very much like the simple inanimate sounds except that they are identified with technical apparatuses that might produce such sounds.
There is always a siren like screeching that gets louder and louder-and
some nights it's almost unbearable
The voice sounds from the ringing of the telephone, in a way wake to it and notice that I am paralyzed.
Two sounds are recurrent. One sound is like air entering a vacuum, it happens sometimes when entering or leaving the state as the ears become functional again. The other sound is like a radio being heard from another room in the house. Many stations at the same time, barely intelligible.
The sound was like high pitched power tools....drills or band-saws that were close to my ears and gained in volume and intensity until I felt like my head was going to explode.
A very loud combination of sounds...a constant crashing, glass breaking, train-like combination.
loud sirens...almost deafening
Sounds - Natural. Alternatively, these sounds may be attributed, perhaps by the less technologically minded, to natural causes.
A gust of wind appears, even though no windows are open
shrill whistling sounds, sound of 'wind'
A rushing/roaring sound like waves in a sea shell almost or maybe similar to white noise.
I felt I was in a sandstorm. I could hear the wind and sand rushing past my ears with a loud (sound) gust of wind
Sounds of Movement. Although the quality of the sounds may be modified slightly when experiencing a ringing sound as a telephone, or a rushing sound as the wind it seems unlikely that the next set of sounds are simple transformations of simple sounds described above. A commonly reported sound is that of footsteps.
Usually, it sounds like someone walking around the apartment. (I live alone.)
There was a sound rather like a cardboard box of some weight being dragged across a dusty wooden floor
Animal Sounds. Similarly, animal sounds of growling, snarling or just barking seem unlikely to be merely elaborations of simple sounds.
I have heard 'growls' like a dog from hell or some other monster!
Can be sounds of an explosion or really loud music or just recently, a sound like a herd of animals howling and screeching
Sometimes sounds of moaning, screaming are reported, Laughing is sometimes
reported as well.
Sounds - Voices - indistinct and/or unintelligible. Symons argues that, in dreams, voices are seldom heard as external sounds. Rather, conversations are experienced "in the head" as internal dialogue. The sense and meaning of conversations in dreams are what are experienced. Bergson (1901/1958) discusses essentially the same idea. "Most of us at one time or another . . . have dreamed about speaking to someone or being engaged in a lengthy conversation only to have forced on us the singular realization that we are not speaking and had not spoken, and that our interlocutor had not uttered a single word. We had exchanged our thoughts and carried on an unequivocal conversation, yet we had heard nothing" (p. 27-28). Bergson further noted that "unless we are provided with some phonic substance, it is hard for us to fabricate sounds in our dreams" (p. 28). In contrast to dream voices SP voices are experienced as definitely externally produced sounds but of indefinite or nonsensical meaning. The voices may be experienced as quite loud shouting or soft whispering but, in either case, the sense of what is being said is elusive.
I heard loud voices and thought there were people outside of my car, but
there were not. (This person reported SP while napping in car.)
I also frequently hear voices saying nonsensical things when falling asleep.
I sometimes hear people (who I think are in the room talking), or music that I think my family or friends are playing.
I heard strange garbled voices whispering in my ears.
moaning and voices
I also frequently hear voices saying nonsensical things when falling asleep.
Loud noises and talking, but I could not make out what was being said.
Vague voices speaking sentences that were nonsense (but in English words)
Usually the sounds are that of people talking or yelling outside. Sometimes it will be a familiar voice like that of my mother. Usually unfamiliar. Many times I will hear high pitched noises, very loud, usually increasing if I don't wake up.
Loud noises and talking, but I could not make out what was being said.
Have had the sense that I was hearing sinister voices - saying nothing in particular.
screaming like sounds
One time I awoke to find half snake/half human thing shouting gibberish in my ears.
On a few occasions it has whispered heavily in my ears. Once it spoke in a language I couldn't understand, the other times I couldn't remember what it had said after I woke up.
Sounds - Voices - distinct. Occasionally the voices may produce intelligible utterances, but these are usually simple commands.
But as I listened I could sense this 'thing' walk to hover over my head-very
close directly over my ear. It said 'Freya!' . . . The voice continued 'I've
got work for you to do!' Then I listened as the presence hovered for
a few seconds more and moved across the room to sit on my roommate's bed.
Sometimes hear voices, e.g., my name being called.
Usually voices. One time he (?) was using my name when speaking to me.
I heard a voice telling me I was playing the game wrong and I had to play it right or quit. it was a woman's voice and she sounded as though she were in a lot of pain and very far away, then she said, he's coming and left.
In one case, a respondent heard the voice of someone who had actually threatened her in the recent past. "But as I listened I could sense this 'thing' walk to hover over my head-very close directly over my ear. It said 'Freya!' At first I thought-just my roomie-but I recognized the voice as a mystery caller who has harassed me twice." This is an interesting instance because we maybe seeing here an example of someone explicitly running through a series of plausible interpretations for this unusual experience and settling on perhaps the most plausible given the context of sensed presence, fear and the recent threatening experience.
Visual imagery in SP is experienced not only less frequently than auditory
experiences but often less vividly. The sense of presence seems to merge
with the less definite visual images. "It was more like an image
than a real presence." Visual imagery seems also to take its cues from
other experiences. Sometimes it is the sensed presence that begins to take
form. "Always accompanied
by the presence, I've seen shapes/beings, from snake/humans type things
that shout gibberish in my ears. I've seen the devil, bats etc. Most of
the time it's a human shape that's completely black." As in the case of
the sensed presence the visual images are almost out of sight, just on
the periphery of vision. "[It was a s]mall ugly creature behind me, which
I could only see from the corner of my eyes."
Sometimes imagery may be associated with the pressure on the chest (See section on "The Incubus"). "Once I had one of this old lady, that was sitting on top my chest beating the living daylights out my head, I pulled myself to and my head was pounding." Not surprisingly, the images may be associated with threats.
Figure is threatening.
Until lately, all my SP involved a visible black shaped 'presence' in my room, meaning to do me harm.
I feel fairly certain that if I let the apparitions get all the way up to me, they will kill me. I have fought out of this to prevent getting too close to the possibility. Each time it happens, I am scared they will kill me, especially if I let them 'take' me out of my body.
On one occasion I felt like a presence and saw a kind of specter. It was a misty form floating above my feet, and I felt that it was the cause of my discomfort.
I once woke up to what I thought was a man leaning over me in bed who had my right arm in a tight grip, holding me down on the bed. The man just had me 'pinned' by the wrist and I was frozen for what seemed like forever staring up into his face (probably lasted less than a minute). The room was dark and the face was in shadows, so I mostly saw an outline of the face. When at last I could move, I whispered 'What do you want?' and the face seemed to just disappear into the flowered pattern of my bedroom drapes. My right arm was 'asleep' and as I then moved it I had extremely painful 'pins and needles' sensation. It was a terrifying experience, but something that never repeated.
The second time, in the first house, I saw a beige roundish being over my bed. The energy was female and it was very, very angry. The second time was the experience above, however, I did not see the presence that was in the room, however, I had visions, that the woman who had died there had. I saw two of her children at the edge of the bed.
I've seen images on the bedcovers.
Once it was an arm reaching out of my floor as if trying to pull itself up, other times it was vague almost faces and movements in my peripheral vision.
The formed shape is usually an unusual geometric shape that floats around the room. I only see this when the room is dark. It used to scare me when I was a child.
Usually larger than me, always male. It never has a face.
There was a woman - whom I could sense but not see - behind me. I feared her. It seemed to be a scene from the past century.
In one of the relatively rare cases of specific and concrete imagery, a Native
American woman drew upon her heritage. Curiously she then adds an apparently
incongruous image of medical personnel.
Spider woman came from the ceiling and wrapped me up and sang songs to me i was l0 and later the deerwoman would come and stand at the foot of my bed and then lab coated people with monitors. I have never been hospitalized. The deerwoman still comes.
For the most part, however, visual images tend to be indefinite and insubstantial. This is in strong contrast to the vividness of visual imagery in dreams (Symons, 1995) and auditory imagery in SP reported above. Visual hallucinations frequently appear to be somewhere between full hallucinations and pseudo-hallucinations. Reed characterizes pseudo hallucinations as lacking the substantiality of externally perceived stimuli and as appearing in inner subjective space. The visual imagery of SP often appear to be less substantial than normal perception but are clearly taken to be perceived in external space.
Some writers appear to require that hallucinations also be believed to be true by those experiencing them (e.g., Reed, 1988). That is, they require that the person be deluded by their experiences. Comments by several respondents suggest that this is a very problematic stance. Many respondents are quite emphatic that the hallucinations are entirely compelling but are able to maintain a critical stance. Their faith in rationality and conventionality triumphs, as it were, over the evidence of their senses. One respondent provided a vivid account of alien abduction, complete with medical procedures, associated with his SP experiences.
At one point, long bony fingers pressed across chest to induce unconsciousness hands picking up and examining mine. Fingernail clippings removed. Painful examinations syringes, devices, exposure of brain, magical 'surgery' sometimes I find that I am like a robot being repaired by human owner. Was COMPLETELY SHOCKED to watch similar scene in Star Trek First Contact. Never seen this scene before my experience but my experience is almost captured in scene with Data getting human skin grafts... WIERD!
This respondent was most emphatic that his experiences were totally compelling but that, considering himself a hard-headed and sensible person, he did not believe any of it for a minute. His experience was of abduction but this did not make it true, even for him.
The present discussion of SP and associated HHEs is much indebted to
the activation-synthesis theory of dreaming (Hobson & McCarley, 1977;
McCarley & Hobson,
1979). According to that theory, REM is initiated via inhibitory activity
of the REM-off cells in reciprocal interaction with REM-on cells (See section
on SP and REM for a more detailed discussion). These brain-stem mechanisms
inhibit motor output and sensory input and provide the cortex with internally
generated activation. The function of the cortical centers is one of synthesizing
quasi-random activation into meaningful patterns. Although the activation-synthesis
model has not emphasized affective components, the pervasiveness of fear
and the sensed presence in the phenomenology of SP indicates that the role
of the amygdala may need to be considered central in understanding the SP
night-mare. We hypothesize that the experience of a threatening presence
during SP is associated with the thalamic projections to the amygdala. During
REM, bursts of activation originating in the brain stem pass through the
thalamus, which has direct projections, not only to specific cortical areas
but also to the amygdala (Charney, Grillon, & Bremner,
1998; LeDoux, 1994). The subcortical thalamo-amygdala pathway provides a
coarse-grained analysis of stimuli sufficient to ensure that dangerous or
threatening events are responded to with emergency reactions without the
delay of detailed analysis via the sensory cortex (LeDoux, 1994, 1996). We
argue that the sense of presence and its strongly associated sense of terror
during SP are a result of activation of the amygdala by bursts originating
in the pontine reticular areas. In normal emergency fear reactions the immediate
sensing of danger is quickly confirmed or disconfirmed. Reciprocal projections
to the polymodal association cortex directly from the amygdala enhance analysis
of critical features of the threatening stimulus corroborate the nature and
seriousness of the threat (Ledoux, 1994). In the absence of exogenous origins,
attempts to analyze the source of fear will inevitably fail to produce corroboration.
Hence the state of apprehensive "suspicion" that
normally might last only milliseconds may last many seconds or even minutes
during SP. Under such conditions subjects might experience a protracted but
insubstantial "thalamic" consciousness (Head & Holmes, 1911; Smythies,
1997) of an indefinite presence strongly associated with fear. The preceding
argument explains the high correlation found between sensed presence and
fear in previous research (Cheyne, Newby-Clark, & Rueffer, 1998, 1999).
When the SP episode persists, the presence may motivate continuing efforts at disambiguation and shape increasingly elaborate interpretations of other HHEs consistent with external threat. These may arise endogenously, via pontine driven oculomotor or middle ear activity, or exogenously, as shadows and ambient sounds. These sensations may be interpreted as approaching footsteps or apparitions that are concrete instantiations of the threatening presence. Such conflict between endogenous and exogenous stimulation is possible because the visual and auditory systems are fully functional during SP (Hishikawa, 1976; Hishikawa & Kaneko, 1965) and hence compete with endogenous sources of activation. This cluster of presence, fear, and auditory and visual experiences consistent with mechanisms underlying responses to predation (LeDoux, 1996) and with a narrative of stalking and threat of attack.